Mekong, Or Cambodia, the chief river of the Indo-Chinese peninsula (Further India), rises near the E. extremity of the main range of the Himalaya mountains, in the S. E. portion of Thibet, flows 8. E. through the Chinese province of Yunnan, the E. part of Burmah, Laos, Siam, Cambodia, and French Cochin-China, and empties through several channels into the China sea near Cape St. Jacques; length, about 1,800 m. In the early part of its course, in Thibet and China, it is called the Lan-tsang; the Burmese call il Kin-lung; while the name Mekong, which has now become its most common designation among Europeans, is locally applied to that longest portion lying in Siamese and Cambodian territory. For about 1,000 m. from its source the Mekong flows through mountainous regions and among some of the most remarkable of the Indian ranges, beginning with the Himalaya proper, and ending with the long chain that extends N. W. and S. E. through the peninsula of Further India. Leaving the main ridge of the latter chain in Laos, in about lat. 18° N, and diverging E. and S. E., it flows through the great central plain of the southern peninsula, irrigating it thoroughly by annual overflows which take place between September and November, and rendering it a region of the greatest fertility.
The navigation of the upper river is difficult and dangerous, its bed, even in the widest parts, being obstructed with shifting bars or projecting reefs. Excepting in the lower portion of its course, rapids are frequent. The scenery along the upper Mekong is of the wildest and most rugged character, the stream often flowing through very deep gorges in the mountains, and in some places tunnelling the cliffs into fantastic forms. For some distance from its mouth, however, the river is navigable even for large vessels, and Panomping, the capital of Cambodia, is easily reached by shipping from the coast. - In 1866-8 the Mekong was explored as far as the borders of Burmah by a French government commission, which made an elaborate report upon the river and its valley. See " Travels in Indo-China and the Chinese Empire," translated from the French of Louis de Carne (London, 1872), and the report of the commission, published in Paris in 1873.